Supporting technical information A98H0003

Associated links (A98H0003)

In-flight entertainment network (IFEN) – Continued airworthiness

Maintenance instructions for continued airworthiness

HI developed and issued the Maintenance Instructions for Continued Airworthiness of Interactive Flight Technologies Inc. Interactive Passenger Entertainment System on Swissair MD11 to comply with FAR 25.1529, Instructions for Continued Airworthiness. This document was released on 20 March 1997 and referenced numerous HI drawings and documents. The maintenance instructions contained the following information:

  • General description of the modification
  • Removal and installation procedures for the LRUs
  • Operating, troubleshooting, and servicing information
  • Frequency and extent of the inspection

Service bulletins

Both IFT and HI were responsible for issuing SBs as required.

Interactive Flight Technologies Inc.

IFT issued 38 SBs, the majority of which were primarily for system software upgrades, movie and content updates, and for product improvement modifications to IFEN components. Some of the product improvements, each addressed by a separate SB, included the replacement of a single blow fuse with a self-resetting circuit protection switch in the cluster controllers, VOD, seat electronics boxes, and management terminal electronics boxes. None of the IFT SBs were considered directly pertinent to the investigation.

Hollingsead International

HI issued 15 SBs for technical changes or improvements to the IFEN system. One SB, applicable by fuselage number to the occurrence aircraft, was considered to be of interest because it involved the installation of additional wiring within the area that was fire damaged in the occurrence aircraft. During the TSB investigators' inspections of Swissair's fleet of MD-11 aircraft, it was observed that the PA wire was installed in various conduits above Galley 2, even though the SB documentation specified the conduit to be used. SB 23-12003-11, Communications-IFT System, PA Key Line Modification, was issued on 2 June 1997 and was applicable by fuselage number to HB-IWF (the occurrence aircraft). HI recommended that this modification, which provided PA audio through the IFEN system, be accomplished during the earliest practical maintenance period. SR Technics could not locate a document referring to this SB, nor was this SB identified in the SR Technics Status List of Engineering Orders. However, HI had performed this modification, at SR Technics facilities, under HI Work Order 67793. An FAA Form 337 was completed by HI on 18 March 1998.

PA system

Detail-Specification for Interactive IFE, Section 5, dated 22.7.96 Rev 1, outlined the PA system requirements. These requirements included the need for the PA signal to override all audio channels of the IFEN system and stop all video, audio, and other functions for the selected PA zone(s). The original IFEN system-to-aircraft integration design did not meet this condition; therefore, HI issued SB 23-12003-11.

Swissair IFEN MM Rev B, issued on 2 September 1997, provided the following information pertaining to the PA system, even though the design was not capable of performing the actions as described:

When the PA system is operated from one of the flight crew [or flight] attendant positions all IFEN activities are paused, and the messages are broadcast simultaneously over the PA and through the IFEN system headphones.

Installation Information

Drawing 50013-103 A/CFootnote 1 Systems to G8 Disconnect and Drawing 50024-101 Relay to G8 Disconnect were to be modified to accomplish this SB.

The SB, with supporting documents, provided the following wire installation information:

  • At the Galley 8 video display unit/relay assembly, install wire WW56-9186-20WH to the new wire run as per Drawing 50013-103/203 (Drawing Change Notice 3186 pg. 4 of 7).
  • Route the wire to the MAR 4 shelf in the E & E bay as per Drawing 20326.
  • Fabricate the 50013-105 wire harness as per the instructions on Sheet 12.
  • Install the harness as per AC 43.13-1A, 2A, the task card, Sheet 6, and the installation drawing on Sheet 10.
  • Route the harness adjacent to the existing cables.
  • The total length of the M22759/34-22-9 22 AWG wire was 107 feet.
  • Fourteen 22 AWG wires were installed.
  • Route the PA wire through conduit ABP7646-51P.
Discrepancies

The TSB identified the following discrepancies:

  • Drawing 50013 Rev G (9-23-98) does not identify Drawing Change Notice 3186.
  • Drawing 20023 Rev B shows wire WW56-9186-20WH located only between pin 36 of the relay assembly and pin 6 of plug P1-7322 located above Galley 8, and not continuing to the MAR 4.
  • The instruction to "install harness per AC43.13-1A" does not provide adequate information as to the specific routing of the wire.

IFEN system maintenance records

All maintenance activities related to the IFEN system were documented in a database. Between the first installation and system deactivation on 28 October 1998, 17 052 discrepancies were recorded for all Swissair aircraft equipped with the IFEN system.

The collected data included aircraft registration information, "trouble" information, "action" information, "date A/C in," and "date A/C out." "Trouble" referred to the recorded discrepancy and "action" referred to the maintenance activity that was carried out to address this discrepancy. For the purpose of evaluation, the TSB defined four data categories and grouped similar entries into the appropriate category.

  1. Reboot: Entries that made reference to a hard or soft reboot, system reset, or both.Footnote 2
  2. Parts Replace: All scheduled and non-scheduled parts replacements.
  3. Software Related: All upgrades and re-installations.
  4. Maintenance Related: Entries such as "plug installed" and "plug replaced" and equipment repairs.

A comparison between HB-IWF and a sampling of the other MD-11 aircraft with the same IFEN system configuration is provided below.

Table: MD-11 IFEN system configurations
Aircraft reg. HB- C-ClassFootnote 3 Installed Date F-ClassFootnote 4 Installed Date Total entries Reboot Parts replace Software Rrelated Maintenance related
IWF 9/97 2/98 620 412 149 23 36
IWI 10/97 10/97 527 258 193 36 40
IWE 4/97 3/98 844 500 271 34 39
IWC 12/97 12/97 629 385 162 14 68
IWK 1/98 1/98 581 361 184 26 10

Power supply failure

One incident was reported of an in-flight trip of a PSU CB. This incident occurred on HB-IWL on 30 August 1998. The PSU 2 CB, F9, located in the lower avionics CB panel, tripped and was reset in-flight but tripped again. When maintenance personnel reset the CB, it immediately tripped and a noise was heard in PSU 2. This PSU was subsequently removed and forwarded to IFT for corrective action. The repair estimation report identified the following:

  • The unit recorded 4 347.4 hours on the front panel power meter.
  • Input terminals were shorted.
  • The J1 connector was burnt and numerous traces were destroyed.
  • The aluminum sheet metal in the vicinity of the J1 connector was melted through.
  • Some unidentified metallic residue found in the vicinity of the melted sheet metal appeared to be foreign to the power supply.
  • Additional assemblies within the unit exhibited several burnt traces.

No detailed examination of the unidentified metallic residue was performed and the reason for the failure was not identified.

FAA policy statement ANM-01-04 – System wiring policy for certification of part 25 airplanes

The FAA released Policy Statement ANM-01-04 on 2 July 2001 to advise applicants for type certificates, amended type certificates, supplemental type certificates, or type design changes on how existing rules, currently contained in 14 CFR, Part 21, are to be interpreted. This notification did not establish any new rules but provided comprehensive guidance on the required elements of a design package and the actions required for compliance. The FAA stated that the policy was necessary to correct deficiencies associated with the submission of design data and instructions for continued airworthiness involving airplane system wiring for type design, amended design, and supplemental design changes. The notification advised applicants of the range and quality of type design data that the FAA expects applicants to submit as part of the certification project.

The FAA did not intend to establish a binding norm with the general policy stated in this document, nor would the FAA apply or rely upon this document as a regulation. However, the FAA expected that those tasked with the responsibility of aircraft certification should generally attempt to follow the policy, when appropriate.

It is and has been the FAA's policy to require that type design data packages submitted for multiple approvalsFootnote 5 include the following elements: a drawing package that completely defines the configuration, material, and production process necessary to produce each part in accordance with the certification basis of the product; any specification referenced by the required drawings; and drawings that completely define the location, installation, and routing, as appropriate, of all equipment in accordance with the certification basis of the product.

Statement of FAA policy

The FAA's Notice of Final Policy, dated 28 January 2002, incorporates changes based on comments received from four sources who responded to the FAA's request for the public to present their views on this policy statement. These changes are identified as footnotes within the applicable section.

The following statements are extracted from the FAA Policy.

Unambiguous definition of configuration:

Type design data packages should completely define the certification configuration.Footnote 6 Specifically, routing and installation of wiring on the airplane should be addressed. It is important that the routing of wiring strictly follow the intent of the criteria established by the FAA in the certification basis as reflected in the original or subsequently approved type design approval holder's design.Footnote 7

System safety assessment:

Certain airworthiness criteria require failure analyses (i.e., failure mode and effect analysis, zonal analysis, or other safety analysis) to demonstrate that a failure of the system under consideration:

  • does not, in itself, constitute an unacceptable hazard, and
  • does not result in damage to other systems that are essential to safety.
Specific Installation Drawings Instead of General References

The FAA expects the applicant to provide definitive drawings instead of merely statements such as "install in accordance with industry standard practices," or "install in accordance with AC 43.13-1A."Footnote 8 The FAA considers such statements as inadequate because the standard practices cannot define the precise location or routing of the wiring.

Process specifications and modifications compatible with original standards

Certain airworthiness requirements require analysis or tests to define the strength, durability, and life of components associated with the installation of wiring in the aircraft (i.e., connectors, brackets, wire constraints, grommets, ground terminations, etc.). These tests and analyses require complete definition of the parts so that:

  • Conformity of the parts to the type design may be verified, and
  • The characteristics of the parts important for test or analysis may be determined.

IFE system STC design/installation

The FAA review of a number of recent certification projects identified various problems, many of which were evident in the IFE system certification documentation, including the following:

  • Not completely defining the specific routing and installation of the wiring, which left a portion of the installation to the discretion of the installer.
  • The practice of referencing general guidance, such as AC 43-13 and industry standard practices, which resulted in an incomplete definition of the installation configuration.
  • Instances in which a modifier is unaware, or does not specify installation and routing practices that are compatible with the certification standards established for the original type design, such as installing a power wire for the modification in a wire bundle containing critical wiring that the original manufacturer was required to isolate from other systems.
  • Maintenance aspects of system wire external to the installed equipment are not being adequately addressed. The integrity of the wiring is typically left to those doing general airplane maintenance, which relies on visual inspections.